1. Field of the Invention
The invention concerns apparatus, methods and compositions for preserving the viability of microorganisms and more particularly concerns an assembly and composition for the protection of anaerobes from exposure to gaseous oxygen during the period of time between isolation from a clinical source and inoculation into a system for culturing and/or identification of the anaerobe.
2. Brief Description of the Prior Art
In recent years there has been an increased awareness of the importance of diagnosing infections caused by anaerobic microorganisms. Apparatus and techniques for culturing and differentiating anaerobic microorganisms has been developed and refined to isolate and differentiate anaerobic microorganisms in an infection site; see for example the apparatus disclosed in U.S. Pat. No,. 3,246,959. However, the weak link in the overall procedure of collecting an anaerobic clinical specimen, carrying the specimen to the laboratory and culturing the anaerobe therein has been in the transportation step. If in transporting the clinical specimen from the patient to the laboratory, the specimen is exposed to gaseous oxygen, the oxygen sensitive anaerobes may die and the subsequent differentiation is inaccurate. Many strains of anaerobic microorganisms are sensitive to oxygen especially in low numbers and may not survive even brief exposures to gaseous oxygen.
A review of the prior art methods and apparatus for transporting anaerobic microorganisms between clinical source and laboratory may be found in the Scope Monograph on Anaerobic Infections published by The Upjohn Company, Kalamazoo, Michigan, (1972; Library of Congress Card No. 72-79754) on pages 54-55. In brief, the reviewed methods describe either rapidly placing a swab containing a specimen into a carbon dioxide filled container or into a transport medium, or aspirate a liquid specimen into a syringe and then injecting the specimen into an anaerobe bottle or vial. The Scope Monograph describes transporting specimens suspected of containing anaerobe microorganisms on cotton swabs protected from exposure to oxygen by immersion in prereduced, anaerobically sterilized Cary-Blair medium in either a tube or a vial with a mineral oil overlay. In addition to the Cary-Blair reduced transport medium there are other commercially available reduced transport media commonly referred to as thioglycolate mediums. These include Amies medium, Stuart's, and thioglycolate- 135C media. However, heretofore the employment of reduced thioglycolate transport media for preserving the viability of anaerobic microorganisms during collection and transport has not been completely encouraging; see for example Yrios et al, Abstracts of the Annual Meeting of the ASM (1974). In general, one of the major problems faced in transporting anaerobic microorganisms resides in maintaining the anaerobes in a viable condition without growth of either the anaerobes or other microorganisms present in the specimen over an extended period of time. This is particularly important for the accurate identification of pathogens whose presence may be masked by the overgrowth of saprophytic microorganisms.
Anaerobic microorganism transporting devices have been described previously; see for example U.S. Pat. Nos. 3,483,089; 3,750,646; 3,773,035; and 3,913,564. In spite of the fairly advanced state of the art, a number of problems remain to deny the art a perfect means of transporting anaerobic microorganisms from a patient to a laboratory. To mention a few, a number of prior art assemblies are not readily shipped without special precautions. A number of assemblies make no provision for preventing desiccation of the transported anaerobes. Many of the transporting devices can be opened only once for access to the contained anaerobes and their usefulness is thereafter lost. The assembly and method of the invention are relatively simple in comparison to the prior art apparatus and methods. The assembly of the invention is constructed readily at low cost and requires a minimum amount of training for operation. In addition, the assembly of the invention may be handled, shipped, and transported without many of the special precautions required of the prior art assemblies. Further, the method of the invention has shown great reliability in operation and assures transportation of viable anaerobic microorganisms even for prolonged periods of time. The assembly of the invention permits one to obtain minimal exposure of a clinical specimen to oxygen. The assembly and method of the invention, in conjunction with the composition of the invention will maintain anaerobic microorganisms viable for several days, without desiccation and without promotion of growth of the anaerobic microorganism or other microorganisms contained in the clinical specimen to be transported. Nor will the number of organisms be diluted by the composition of the invention because of the firmness of the composition in contrast to prior art compositions which are fluid or semi-solid in nature. Access to the transported anaerobes within the assembly may be had a plurality of times without compromising the performance of the invention. The composition of the invention is particularly advantageous in that while maintaining viability of anaerobic and other organisms, growth of microorganisms contained in the specimen is not promoted by the medium. Other advantages of the invention will be described in greater detail hereinafter.